Phenol and cyclohexanone are important materials in the chemical industry and are useful in, for example, the production of phenolic resins, bisphenol A, ε-caprolactam, adipic acid, and plasticizers.
Currently, a common route for the production of phenol is the Hock process. This is a three-step process in which the first step involves alkylation of benzene with propylene to produce cumene, followed by oxidation of cumene to the corresponding hydroperoxide, and then cleavage of the hydroperoxide to produce equimolar amounts of phenol and acetone. However, the world demand for phenol is growing more rapidly than that for acetone. In addition, the cost of propylene feed is generally high.
Thus, a process that uses alternative feeds and coproduces higher-value ketones, such as cyclohexanone, rather than acetone may be an attractive alternative route to the production of phenols.
It is known from, e.g., U.S. Pat. No. 6,037,513 that cyclohexylbenzene can be produced by contacting benzene with hydrogen in the presence of a bifunctional catalyst comprising a molecular sieve of the MCM-22 type and at least one hydrogenation metal component selected from Pd, Ru, Ni, Co, and mixtures thereof. This reference also discloses that the resultant cyclohexylbenzene can be oxidized to the corresponding hydroperoxide which is then decomposed to the desired phenol and cyclohexanone co-product.
In the hydroalkylation step, both the conversion of the aromatic compound (e.g., benzene) and the selectivity of the target alkylated aromatic compound are substantially determined by the performance of the hydroalkylation catalyst. Hydroalkylation using a catalyst comprising MCM-22 molecular sieve and a hydrogenation metal component can result in quite substantial amounts of dicyclohexylbenzene and tricyclohexylbenzene due to over alkylation of cyclohexylbenzene. There is a need for an improved catalyst and hydroalkylation process that with reduced over alkylation without sacrificing cyclohexylbenzene yield.